Transmission modulation apparatus

Abstract

A transmission modulation apparatus capable of dealing with characteristic variations of a high-frequency power amplifier without always forming an amplitude loop. Transmission modulation apparatus 100 is configured with level detector 140 that receives input of a level detection control signal and detects the output signal of high-frequency power amplifier 130 , and offset voltage correcting section 150 that corrects an offset voltage using collinear approximation including a first point where the relationship between the power supply voltage value and the output voltage starts to shift from linear to non-linear based on an output signal of level detector 140 and a second point where output voltage is a minimum. Offset voltage correction is adaptively executed, and linearity between the voltage value of the baseband amplitude signal and the output voltage of high-frequency power amplifier 130 when the voltage value of the baseband amplitude signal is low is compensated.

1. A transmission modulation apparatus comprising:
 an amplitude/phase data generating section that generates a baseband amplitude signal and a baseband phase signal; 
 a phase modulator that phase-modulates a high-frequency signal using the baseband phase signal; 
 a high-frequency power amplifier that amplifies an output signal of the phase modulator based on an output signal from a power supply voltage control section; 
 the power supply voltage control section that calculates a power supply voltage value for controlling a power supply voltage of the high-frequency power amplifier based on the baseband amplitude signal, adds a predetermined offset voltage to the power supply voltage value, and outputs the result to the high-frequency amplifier as the output signal; 
 a determining section that determines from execution conditions whether or not offset voltage correction for correcting the offset voltage is performed; and 
 an offset voltage correcting section that, when the offset voltage correction is determined to be performed by the determining section, corrects the offset voltage using a first line, obtained by collinear approximation in a region where a relationship between the power supply voltage and an output voltage of the high-frequency power amplifier is non-linear, having a different slope from a slope of a second line in a region where the relationship is linear. 
 
     
     
       2. The transmission modulation apparatus according to  claim 1 , wherein the determining section determines that the output signal level of the high-frequency power amplifier is less than a predetermined voltage. 
     
     
       3. The transmission modulation apparatus according to  claim 1 , wherein the determining section determines the high-frequency power amplifier output voltage where the relationship between the power supply voltage and the high-frequency power amplifier output voltage starts to shift from linear to non-linear. 
     
     
       4. The transmission modulation apparatus according to  claim 1 , wherein the determining section determines a temperature change of the high-frequency power amplifier. 
     
     
       5. The transmission modulation apparatus according to  claim 1 , wherein the determining section determines a usage time, energized time or power supply timing. 
     
     
       6. The transmission modulation apparatus according to  claim 1 , wherein the offset voltage correcting section corrects the offset voltage using the first line obtained by the collinear approximation and including a first point extracted from the region where the relationship is linear and a second point extracted from a region ranging from where the relationship starts shifting from linear to non-linear to where the high-frequency power amplifier output voltage is a minimum. 
     
     
       7. The transmission modulation apparatus according to  claim 1 , wherein the offset voltage correcting section corrects the offset voltage using the first line obtained by the collinear approximation and including a first point where the relationship starts shifting from linear to non-linear and a second point where the high-frequency power amplifier output voltage is a minimum in the region where the relationship is non-linear. 
     
     
       8. A transmission modulation apparatus comprising:
 an amplitude/phase data generating section that generates a baseband amplitude signal and a baseband phase signal; 
 a phase modulator that phase-modulates a high-frequency signal using the baseband phase signal; 
 a high-frequency power amplifier that amplifies an output signal of the phase modulator; 
 a power supply voltage control section that calculates a power supply voltage value for controlling a power supply voltage of the high-frequency power amplifier based on the baseband amplitude signal; 
 a determining section that determines from execution conditions whether or not phase correction for correcting a phase of the baseband phase signal is performed; and 
 a phase correcting section that, when the phase correction is determined to be performed by the determining section, corrects the phase of the baseband phase signal using a first line, obtained by collinear approximation in a region where a relationship between the power supply voltage and an output phase of the high-frequency power amplifier is non-linear, having a different slope from a slope of a second line in a region where the relationship is linear. 
 
     
     
       9. The transmission modulation apparatus according to  claim 8 , wherein the phase correcting section corrects the phase of the baseband phase signal using the first line obtained by the collinear approximation and including a first point, the first point being the output phase of the high-frequency power amplifier corresponding to an output voltage of the high-frequency power amplifier in the region where the relationship between the power supply voltage and the output voltage of the high-frequency power amplifier is linear, and a second point, the second point being the output phase of the high-frequency power amplifier corresponding to the output voltage of the high-frequency power amplifier in a region ranging from where the relationship between the power supply voltage and the output voltage of the high-frequency power amplifier starts shifting from linear to non-linear to where the output voltage of the high-frequency power amplifier is a minimum. 
     
     
       10. The transmission modulation apparatus according to  claim 8 , wherein the phase correcting section corrects the phase of the baseband phase signal using the first line obtained by the collinear approximation and including a first point, the first point being the output phase of the high-frequency power amplifier corresponding to a point where the relationship between the power supply voltage and an output voltage of the high-frequency power amplifier starts shifting from linear to non-linear, and a second point, the second point being the output phase of the high-frequency power amplifier corresponding to a point where the output voltage of the high-frequency power amplifier is a minimum in a region where the relationship between the power supply voltage and the output voltage of the high-frequency power amplifier is non-linear.